1. Field of Invention
This invention relates to threshing and cleaning systems for combine harvesters, and more particularly, to method for managing the airflow of a blower mechanism through the threshing and cleaning systems of the combine harvester.
2. Description of Related Art
Combine harvesters have a threshing mechanism for threshing the harvested crop and a cleaning system used to remove chaff and other residue from the threshed crop. In one example, a rotor cooperates with concaves to thresh the harvested material, and initial separation occurs as grain and smaller residue are pushed through the grated concaves by centrifugal force to the cleaning system. Large residue pieces such as stalks and stems continue to move rearwardly and are eventually discharged out the rear end of the rotor assembly where it is acted upon by a chopper or spreader and deposited on the ground.
Within the cleaning system, oscillating sieve assemblies in conjunction with air flow remove the chaff from the threshed grain, which gravitates through the chaffer and sieve assembly to an oscillating clean grain pan. The clean grain pan, in turn, directs the clean grain to a discharge auger that elevates the grain to an onboard storage bin. A second oscillating pan directs materials other than grain over the edge of the bottom sieve assembly to a different discharge outlet for recirculation back through the threshing, separating and cleaning apparatus to extract the previously unthreshed grain.
A blower may be used to produce an airstream that entrains the lighter non-grain particles and carries them out the rear of the harvester. However, it can be challenging to control the airflow from the blower to get an even distribution of air across both the threshing mechanism and the cleaning system.